1. Field of the Invention
The present invention relates to the field of etching, the field of photolithographic etching, the photolithographic etching of non-planar surfaces, and photolithographic etching using fiber optic arrays to direct imaging radiation against a photoresist surface.
2. Background of the Art
Etching is a process with a long history that has developed utilities in a wide array of different technologies. Even chiseling is a mechanical form of etching, used thousands of years ago to put writing and glyphs into stone. The use of stencils to apply inks or paints was the next progression towards the modem format for sophisticated etching known as photoresist or photolithographic etching. In the photolithographic format of etching, a photoresist composition is place over a surface onto which or into which an etched pattern is to be introduced. The photoresist composition has two primary functional properties. It forms a film that can be subjected to radiation (e.g., X-ray, UV, visible, near infrared, or infrared radiation) that will alter the solubility or areas where sufficient radiation is absorbed. The alteration in solubility will be either an increase in solubility where radiation is absorbed (a positive-acting photoresist system) or a decrease in solubility where radiation is absorbed (a negative-acting photoresist system). After an appropriate amount of radiation in an image-wise distribution or pattern, the irradiated photosensitive film is washed or developed in a solvent that can differentiated between the different levels of solubility created in the photoresist film by the irradiation. Usually the developing of wash-off solution (referred to as the developer) is preferably an aqueous solution (e.g., a water-based alkaline solution, or aqueous solution with small amounts of alcohol, such as n-butanol), although organic solvent solutions may also be used. The developer or wash-off solution or liquid (as pure water wash-off systems have been prepared) removes regions of the photoresist composition that are relatively more soluble than the other regions (that have been irradiated in a negative acting system or which have not been irradiated in a positive acting system). The removal or the image-wise distribution of photoresist composition leaves a pattern or image of photoresist material that must now display its second fundamental property.
The remaining photoresist composition must resist the solubilizing activity or etching activity of an etchant solution that is used to etch features into the surface. This etchant solution may be relatively stronger and is usually fundamentally different than the nature of the developer solution (e.g., the tech solution may be strongly acidic, contain chelating agents, may be at elevated temperatures, may be water-based or organic solvent based, and may be a complex mixture of many ingredients). The photoresist composition must be able to endure the effects of the etchant solution at least as long as is necessary to enable the degree of etching of the substrate surface as is desired by the operator. These properties are not easily obtained, and much effort has been put into developing photoresist compositions that can perform these and other functions, and provide sufficient resolution (e.g., etch lines of as little as 1 micrometer and less) to enable use of the technology in the manufacture of sophisticated devices such as stents, catheters, microcoils, circuit boards, circuits, chips, light control films, medical devices, and the like.
The photolithographic process can be highly economical with regard to large volume production of elements and devices with extremely detailed surface structures or holes required. However, the capitol investment in equipment and the skill of the operators is likely to be commensurately high with the precision required in the article and the process.
The exposure methods for such systems usually involve the application of high resolution masks over the photoresist compositions, the use of laser imaging systems, the use of printing compositions for the application of masks, and other relatively high resolution imaging systems.
U.S. Pat. No. 5,181,130 describes a novel liquid crystal display which includes a layer of liquid crystal material, a thin transparent layer, one or more polarizers, and a fiber optic faceplate. The fiber optic faceplate serves to allow ambient light from a much wider range of incident angles to illuminate the LCD than would be the case with prior art LCDs, and allows the viewer to position himself so as to avoid front surface glare and still see the display brightly illuminated, even in difficult lighting situations. Hoffman et al. were one of the first to couple fiber optic panels with Liquid Crystal Diodes (LCDs) as shown in U.S. Pat. No. 4,349,817. U.S. Pat. No. 5,181,130 asserted that application of the teachings of Hoffman et al. would not improve, and in fact would seriously degrade, the contrast of LCD displays for two reasons. First, eliminating light which strikes the display at angles to the display surface normal greater than the viewing angle of the display will not enhance the contrast because displays depend upon the action of polarizers on polarized light propagating within the display rather than scattering to produce the light and dark areas of their images. Second, introduction of a fiber plate, as taught by Hoffman et al., in near-contact with the liquid crystal layer itself will seriously reduce the image contrast because light passing through such a fiber plate is strongly depolarized, thus largely destroying the distinction between the light and dark areas of the image.
U.S. Pat. No. 5.095,202 teaches that a proximity image intensifier for intensifying an optical image may comprise:
a faceplate having a surface for receiving the optical image and another surface; a photocathode fixed to the another surface of said faceplate for photoelectrically converting the optical image and producing photoelectrons; a fiberplate having a surface closely disposed in confrontation with said photocathode; a phosphor screen fixed to the surface of said fiberplate for receiving the photoelectrons from said photocathode and producing an intensified optical image thereon; a high-voltage power supply for applying a high voltage necessary for accelerating the photoelectrons moving toward said phosphor screen; a power supply path connected between said photocathode and said high-voltage power supply and between said phosphor screen and said high-voltage power supply for connecting said high-voltage power supply across said photocathode and said phosphor screen; and a resistor interposed in said power supply path at a position immediately before at least one of said photocathode and said phosphor screen for suppressing an excessive photoelectric current which may flow between said photocathode and said phosphor screen when highly intensive light is locally incident on the surface of said faceplate.
U.S. Pat. No. 6,019,784 describes an expandable stent useful for implantation into an artery or the like. The stents are made using electroforming techniques in which an electrically-conductive mandrel is coated with a suitable resist material, after which the resist is exposed to an appropriate light pattern and frequency so as to form a stent pattern in the resist. The mandrel is then electroplated with a suitable stent material. The mandrel is etched away once a sufficient layer of stent material is deposited, leaving a completed stent. The preferred exposure system of one embodiment comprises a controller, which may be a computer or similar device, operably connected to light emitting diodes (LEDs) that are coupled to optic fibers. The optic fibers are routed to a mounting fixture. The optic fibers and future together form an exposure ring which surrounds the mandrel. The optic fibers are used to direct light to the resist coating on the surface of the mandrel and thereby create a stent pattern in the resist.
U.S. Pat. No. 6,086,773 describes a process for the manufacture of flexible tubular elements, particularly stents for the medical field, the process comprising the steps of: a) providing a hollow metal tube (or metal coated tube) with an open pattern of a chemical-etch-resistant coating layer; b) supporting the hollow metal tube with a coating thereon onto a chemical etch resistant support element; c) contacting the open pattern with a solution capable of etching the metal of the hollow metal tube so that said metal is etched away from physically exposed surfaces of the metal tube and openings in the metal tube corresponding to the open pattern of the coating layer are created in the metal tube element without etching the chemical etch resistant support element; and d) removing the metal tube from the chemical etch resistant support element. U.S. Pat. Nos. 6,107,004; 6,027,863; 5,898,706; 5,817,243; and 5,741,429 also show alternative methods for photoexposing resist materials and subsequent etching of surfaces through pattern residues of resist materials.
Prior art in fiberoptic (FO) faceplates involve placing them onto display devices for the purpose of optical coupling the display screen to an optical system, or using them in high brightness direct view displays. CRTs have been manufactured with fiberoptic plates, which focuses and relays the image from the CRT to a light valve or large screen projection system. U.S. Pat. No. 4,591,232 of Jeskey disclosed fiberoptic CRT faceplates that have light absorbing black fibers dispersed throughout the bundle to reduce xe2x80x9chalationxe2x80x9d or xe2x80x9cballooningxe2x80x9d of the image. U.S. Pat. No. 4,573,082 of Jeskey disclosed a similar CRT fiberoptic faceplate for optical transfer of an enhanced image to a projection screen. In addition, European Patent 0122829 of Rover et. al. disclosed a fiberplate to act as an optical filter in order to provide optimum visibility of a display device under a variety of ambient viewing conditions. The primary shortcoming of these prior art display devices is that they do not disclose or anticipate pen/stylus input means integrated with a display. This puts such display devices at a severe disadvantage in the highly interactive computer, display, and PDA markets.
The majority of photoresist systems are used in the manufacture or treatment of two dimensional objects (such as printing plates or etched flat surfaces). Although some systems, as described above, are designed for the etching of three-dimensional articles, these systems can be relatively expensive and capital-intensive and labor intensive. It would be desirable to provide a photoresist etch system that can be used with facility in the rapid manufacture of three-dimensional objects, without large capital investment and without the need for sophisticated training techniques and highly skilled technicians.
A photoresist etching process and system that can be used for the etching of non-planar or three-dimensional surfaces comprises a non-planar shaped fiber optic array or fiber optic panel. The array or panel has a contour or shape that may nest a non-planar or three-dimensional article or surface. The non-planar or three-dimensional article or surface has a photoresist composition on its surface facing the optical fibers of the fiber optic array or panel, and the article or surface is nested against the contour or shape of the array or panel. Radiation is transported through the optical fibers and exposes the photoresist composition. The optical fiber array may perform an image-wise exposure of the photoresist composition by appropriate blockage of the radiation before it enters or as it enters a distal end of the optical fibers. In this manner, an image-wise distribution of radiation is presented against the photoresist composition, and an image-wise developable resist pattern is created on the non-planar or three-dimensional article or surface. This process can be used on cylinders, tubes, spheres, undulating surfaces, blocks, wavy surfaces, stepped surfaces, and any other shape that can be standardized or formatted into a nesting shape.